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CB, FRS, GMRS, MURS - choosing a type of personal communication service seems to involve a puzzling alphabet soup of different types of radio products.

What does it all mean, and which is best for you?

 
 
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Personal Radio Communication Services

These two walkie-talkie type radio handsets offer 22 combined GMRS and FRS channels and list for only $39.99. Others can be found for even less.

Handheld two way radios are today an incredible bargain, but only if they work as you expect and need them too.

Part 1 of a 5 part series - click for Parts  One  Two  Three  Four  Five

 

 

CB radios experienced a sudden burst of fame - or infamy - during the late 1970s, with the song 'Convoy' and a string of movies such as 'Smokey and the Bandit'.

Today, CB radio service is largely defunct (other than for truckers), but new types of radio services - notably FRS - provide similar or better service for individuals and families wanting a convenient way to keep in contact over relatively short distances.

In this first part of a new series on personal radio services, we explain the different types of radio service available to you. In the second part we discuss the theory of what determines the effective range of these radios. In the third part we test out CB, FRS and GMRS radios and tell you which services give the best range and convenience.

Typical Uses for these types of radios

All these different types of radio services are intended to be used for short range communications - typically of no more than a mile or two. If you are with other family members at a Shopping Mall, or at some type of Outdoors Event, in theory these radios will enable you to all keep in touch with each other.

The radios can also be helpful if you are traveling with friends in two (or more) cars. You can easily keep in contact if you get separated (as long as not too much distance gets between you), and discuss where you'll stop and plan for turns and get in the correct lane in plenty of time.

These radio services are unlimited and free (except for the need to buy an annual license for GMRS) and work anywhere without the need to use cellphone type external transmitting towers or other equipment. This can make it very convenient whenever you want quick easy short range communications.

With the possible exception of CB, none of these services work over anything other than very short range. CB sometimes reaches out as far as 10-15 miles (and in special circumstances, can travel hundreds of miles).

What the Acronyms Mean

The four types of radio service we're looking at are :

CB

  • Citizens Band radio.

  • This is an AM service with 40 channels that operates at approximately 27 MHz.

  • Maximum power of 4 Watts.  Can have separate antenna (for better signal).

  • If operating in SSB mode can have 12 Watts of PEP (= slightly better range).

  • Few handheld radios manufactured now - mainly sets for in-car or at-home use.  Handheld sets have large aerials.

  • Can be used for business or personal use.  No license required.

FRS

  • Family Radio Service.

  • This is a low power FM service with 14 channels that operates at approximately 462.5 MHz and 467.5 MHz (channel frequencies are in the mid-points between the GMRS frequencies).

  • Maximum power of 0.5 Watts.  No separate antenna.

  • Cheapest type of radios.  Only handheld sets made.

  • Can be used for business or personal use.  No license required.

GMRS

  • General Mobile Radio Service.

  • This is a higher powered FM service with 8 duplex or 16 simplex channels (in theory, but usually only the 8 lower frequency bands are used, the upper 8 are used to transmit to repeaters) that operates at similar frequencies to FRS (around 462.5MHZ plus a matched duplex channel around 467.5MHz).

  • Maximum power of 50 Watts.  Can have separate antenna.

  • Also can operate on seven of the frequencies (the 462.5MZ set) used by FRS, with maximum power of 5 Watts (but FRS radios on the same frequencies are limited to 0.5 Watts).

  • Advanced sets can be used with relay/repeater stations to give greatly increased range.

  • For personal use only, not for business use.  FCC license required.

MURS

  • Multi-Use Radio Service.

  • This is the newest of the four services, and is an FM service with five channels operating at approximately 153 MHz.

  • Maximum power of 2 Watts.  Can have separate antenna.

  • Most expensive type of radios (currently) but will probably come down in price as becomes more popular.

  • For business and personal use.  No license required.

Frequencies

It is interesting to compare the frequencies of different types of other radio services so as to see where the above set of frequencies are in relation to other types of radio service.

(Note that 1 MHz means 1 megahertz and is one million cycles per second, and 1 GHz means 1 gigahertz and is one billion cycles per second.)

Human hearing

20 Hz - 20kHz (0.00002 - 0.02 MHz)

AM

AM radio stations broadcast between 0.5 and 1.5 MHz.

Shortwave radio

Most long distance shortwave radio is in the 2.3 - 30 MHz range, and broadcast in AM

FM

FM radio stations broadcast between 88 and 108 MHz.

Weather Service

The seven weather service radio channels broadcast around 162 MHz.

TV

Channels 2-6 operate between 55 - 88 MHz.
Channels 7-13 operate between 175 - 215 MHz.
Channels 14 - 83 operate between 471 - 890 MHz.

Cordless Phones

Most cordless phones these days work on either 900 MHz or 2.4 GHz (= 2400 MHz).  Older phones work on lower frequencies.  New phones are now being released that work on 5.8 GHz

GPS Navigation Service

GPS satellites broadcast a signal on two frequencies, 1575.42 MHz (L1) and 1227.6 MHz (L2).

Cell Phone

Cell phone services operate between 800 - 900 MHz and between 1800 - 1900 MHz.
New '3G' cell phones work around the 2200 MHz frequency.
 

Satellite phone service

Satellite phone service uses L band frequencies around 1.62 GHz.

Satellite radio - XM Radio and Sirius

Satellite radio uses a narrow band of frequencies around 2.3GHz, which is part of the 'S band'.

Wi-Fi
Bluetooth
Microwave ovens

2.4 GHz (= 2400 MHz).
Also used by some cordless phones.

Satellite tv

C band satellites - using the older big dishes, use 3-7 - 4.2 GHz.
Ku band satellite systems - the new digital systems with small fixed dishes - use 10.7 - 12.5 GHz.

Police Radar Guns

Police radar guns operate in three frequency bands :

X band is the oldest, and is about 10.5 GHz.  It is also used by many other devices such as motion detectors for automatic doors and burglar alarms.
K band is 24 - 24.25 GHz and is the most common band in use.
Ka band is the newest frequency band and is less commonly found.  It ranges from 33.4 - 36 GHz.

 

Public and Not so Public Radio Services

In simple terms, there are four main types of radio services that people use :

  1. Services that require the operator to pass an exam (eg ham radio licenses)
  2. Services restricted to business users only
  3. Services open to the general public (and which may or may not also allow business use) for which an annual license needs to be purchased (but no exams need be passed - all you do is fill out a form and pay a fee)
  4. Services open to the general public (and which may or may not also allow business use) for which no licensing is required and for which no annual fee needs to be paid

For the purpose of these articles, we will ignore the first two categories. Thee four services we are reviewing are either type 3 (GMRS) or type 4 (the other three).

If you have other needs - for example, if you have a boat or plane, then other types of radio communications may be better for you (and sometimes might be mandatory).

Because these four types of radio service are public, anyone with a radio tuned to the same channel can listen in on what you are saying.

A worse feature is that you have to share that channel with other users, too. Sometimes, and in some places, some channels will be very busy with lots of people using the channel (and often for incredibly stupid things, or so it seems to other people impatiently waiting to use the same channel) and it can be almost impossible for you to use it yourself.

It is also a nuisance when you're trying to carefully listen out for a radio transmission from a friend, and instead you're all the time hearing other broadcasts from other people.

For this reason, it is good to have an agreed arrangement so that if the channel you normally use is busy with other users, you have a planned alternate channel you know to go and use instead. Some radios also let you monitor two channels simultaneously, making it easier to catch calls from your friends, whichever channel they are using.

Privacy Codes

A partial solution to the annoyance of lots of other people talking on the same channel is the use of so-called privacy codes - known as CTCSS or DCS (Continuous Tone Coded Squelch System or Digital Coded Squelch, if you must know!). This enables you to tell your receiver only to listen to particular transmissions, and to ignore all others. There are 38 different CTCSS codes and 83 different DCS codes available for each radio channel, making it easy for you to assign a code to the people you want to talk with that probably no-one else will be using at the same time.

Although these codes are sometimes referred to as 'privacy' codes, they are NOT privacy codes. They don't stop anyone else from listening in on your conversation. They only stop you from listening in on other people's conversations! If someone else is on the same channel, but without activating their CTCSS/DCS feature, they can still hear everyone's conversations, no matter what type of coding they are using.

There is also a potential problem with these codes - you might not realize that someone else is using the channel before trying to use the channel yourself.

What Happens if Two People Transmit at the Same Time

If two people transmit at the same time on an AM (CB) radio frequency, people listening to the channel will probably hear neither person. Instead, they'll just hear a high pitched squeal caused by the two radio signals interfering with each other.

If two people transmit simultaneously on an FM (FRS GMRS MURS) radio, then usually the stronger of the two signals will block the weaker signal. You'll only hear the stronger signal, the quieter signal will be rejected entirely.

Simplex or Duplex

Two way radios are either simplex or duplex. A simplex service is one where you send and receive (ie listen and talk) on the same frequency. A duplex service is where you send (talk) on one frequency but receive (listen) on a different frequency.

A duplex service has two capabilities that a simplex service does not. Firstly, a duplex service can be used so that you can simultaneously talk and listen at the same time - just like on a telephone or cell phone, which are duplex services.

Secondly, a duplex service can be used with a repeater station. A repeater station is usually situated somewhere with good coverage, and has an excellent aerial system, sensitive receiver and high power transmitter. It rebroadcasts signals that it receives, but on a different frequency. The repeater gives much longer range coverage.

All four radio services are 'simplex' systems, although GMRS can also be operated in duplex mode (if you have a duplex capable radio set and access to a repeater).

There are also some inexpensive (about $20) very short range (about 100 yds) duplex CB radio systems (basically they are two walkie-talkies connected together so that one is transmitting on one channel, and the second is listening on a different channel, and vice versa on the other pair).

PTT or VOX

Most radios are PTT - Push to Talk. In order to transmit, you have to push a button, and then, when you have finished speaking, you release the button.

Some radios also have a VOX feature. This is a Voice Operated Transmitter - the microphone is listening and any time it hears sounds, it automatically switched the radio to transmit.

A VOX feature seems to be really clever and convenient, and sometimes there are situations where you have both hands busy, but need to be able to use the radio too. But, in practice, most of the time, these features do not work well.

They either do not detect your voice when you start to talk, or else, many other random sounds also trigger the VOX circuit, with the result being that your radio is transmitting unnecessary rubbish a lot of the time, annoying other users of the channel, and using up your batteries faster than necessary.

We recommend you do not use the VOX feature on radios unless you're in a special situation where it is essential.

Accessories

A useful accessory can be a combination earpiece/microphone.

If you're using rechargeable batteries (sometimes a good idea, but sometimes also a bad idea - see part 2) then you'll want some sort of battery recharging unit as well.

Using Special Words and Phrases on the Radio

You don't need to start using special 'CB-slang' when using these radios. The idea of all these radio services (even, in theory, including CB, too!) is that you use them only to talk to people that you already know, and all you need do is speak normally, the same as when chatting in person.

If you have GMRS radios, you need to give your official call sign every 15 minutes or so, but with the other radios, you don't need any special identifiers or anything. Just talk any way you want to.

Read more in Parts 2, 3 4 & 5

In Part 2 we discuss how it is that manufacturers can claim ranges of 'up to seven miles' when the effective range - as tested by us - is sometimes as little as one twentieth the claimed range. Many factors influence maximum range - some we can influence, most we can not. In particular, read the startling truth about the importance of transmitter power to give you more range.

In Part 3 we report on real world test results of 'consumer grade' radios and help you choose which is the best system for your needs.

In Part 4 we repeat the testing, this time using 'professional grade' radios to determine just how much more performance you get from these much more expensive radios.

In Part 5 we explain the confusing mismatch of channel number allocations to different FRS/GMRS radios.
 

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Originally published 27 June 2003, last update 19 Dec 2013

You may freely reproduce or distribute this article for noncommercial purposes as long as you give credit to me (David Rowell - KF7VVM) as original writer.

 
 
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Personal Radio Service explained
Factors influencing radio range
Range Testing and Results - Consumer grade radios
Range Testing and Results - Professional Grade Radios
FRS/GMRS frequencies explained and decoded
All About Radio Repeaters
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